1. Field of the Invention
The present invention relates to clips for supporting insulators in electric heaters. More particularly, this invention relates to a flat metal clip for supporting a flat ceramic insulator which has at least one closed or open hole for retaining an electrical resistance heating coil.
2. Statement of the Related Art
The use of round bushing or barrel-shaped ceramic insulators to support electric resistance heating coils, which are xe2x80x9cstrung throughxe2x80x9d the bushings, is well known in the prior art. The use of flat ceramic insulators with either a closed hole or an open-ended hole at each end of the insulator to support electric resistance heating coils is also known in the art. Also known in the art are flat insulators with only one closed or open-ended hole, often referred to as xe2x80x9chalf insulatorsxe2x80x9d.
Bushing insulator supports require at least one bushing ceramic insulator at each support point for the resistance heating coil, and a metal support for holding each insulator. On the other hand, flat insulators with a closed or open-ended hole at each end can support an electric resistance heating coil at both ends of the insulator.
However, electric heaters which use flat ceramic insulators with a closed or open-ended hole to support the heating wire have two substantial problems. The first problem occurs when the insulator is at the end of the metal support structure, where the electric resistance coil passes through one hole in the insulator, then is reversed and passed through the hole in the opposite end of the insulator. In the existing designs of this type, the metal structure supporting the flat ceramic insulator may incur a risk of a short circuit due to insufficient clearance between the electric heating coil and the metal insulator support.
The second problem with existing flat, two-hole ceramic insulators is that the insulators and existing metal insulator supports cannot be made with a narrow profile, as is possible with electric heaters which use bushing insulators. In particular, the metal insulator supports have a width which is significantly greater than the width of the flat insulator.
An embodiment of the present invention is a substantially flat metal clip for supporting one or two insulators, particularly flat ceramic insulators having at least passage for supporting an electric resistance heating coil.
One example of this embodiment connects two insulators to a rail of an electric heater frame, and includes a insulator-support clip which comprises a main body having a center axis and structural member for securing to the rail. A first flange extends from the body perpendicular to the center axis. The first flange has a first cut-out for accommodating a first insulator. The first cut-out has an open end with a first width in the extending direction of the flange, an abutment edge spaced a first support depth from the open end, an inner edge proximal to the body and an outer edge spaced the first support width from the inner edge. A first pair of bendable tabs is attached to the first flange, each bendable from a respective first position to a respective second position, positioned at respective ends of the open end of the first cut-out. The first pair of bendable tabs, when each is in its first respective position, permits insertion of the first insulator into the first cut-out and, when each is bent to its respective second position, constrains the first insulator within the first cut-out.
A second flange, having a second cut-out to support a second insulator, and preferably formed identical to the first flange, extends from the body in a direction opposite from the first flange. The second flange has a second pair of bendable tabs disposed at respective ends end of the open end of the second cut-out. Like the first pair of bendable tabs, the second pair of bendable tabs, when each is in its first respective position, permits insertion of the second insulator into the second cut-out and, when each is bent to its respective second position, constrains the second insulator within the second cut-out.
In a first aspect of this embodiment the structural member for securing to the rail is a channel extending along the central axis, having a cross-section that accommodates the cross of the rail, whereby the rail is welded to the channel.
In a second aspect of this embodiment the structural member for securing to the rail is a pair of T-shaped structures, each aligned on the central axis, each having a pair of bendable flaps extending outward from the central axis, the bendable flaps shaped and dimensioned for bending around and clinching the rail.
One feature of this second aspect is the pair of bendable flaps being formed to bend around and clinch a rail having a T-shaped cross section.
A further embodiment of this invention is in substantial accordance with either of the first and second aspects, but having only one flange, for supporting a single insulator.
A further aspect of the present invention is a clip/insulator assembly including any of the above-summarized aspects or embodiments of the inventive clip, supporting either one or two flat ceramic insulators, each insulator having at least one passage for supporting an electric resistance heating coil.
Another aspect of the present invention is a clip/insulator/rail assembly including any of the above-summarized aspects or embodiments of the inventive clip, supporting either one or two flat ceramic insulators, each insulator having at least one passage for supporting an electric resistance heating coil, the clip being secured to a frame rail of an electric heater.
A still further aspect of the present invention is an electric heater comprising the clip/insulator/rail assemblies of this invention.
Another aspect of this invention is that the insulators for securing within the inventive clip may be formed as half insulators, which have as few as one passage for supporting a heater coil. Still further, the inventive insulators for secure mounting with the inventive clips may be formed with either open or closed passages for supporting the heating coils.
The unique metal clips of this invention, used in conjunction with the aforementioned types of flat insulators, eliminates the need for ceramic bushing or barrel-shaped insulators.
Therefore, a primary object of this invention is to provide an insulator-support clip which has a low profile structure that eliminates interference between the heater coils and the metal frame in an electric heater.
A further object of this invention is to provide an insulator-support clip which permits replacement of round, bushing or barrel-type insulators with flat open or closed-ended ceramic insulators.
Another object of this invention is to provide an insulator-support clip which can be used with a variety of metal frames in electric heaters.
A still further object of this invention is to provide an insulator-support clip which facilitates automated assembly of the electric heaters when clamped to unique metal T-bar support rails.